Indicating apparatus for locomotive back pressure



NOV. 26, 1929. E, PEARCE ET AL I NDICATI NG APPARATUS FOR LOCOMOTIVEBACK PRESSURE I Filed Oct. 21, 1925 2 Sheets-Sheet l 3 IIH'III' Nov. 26,1929. s, PEARCE ET AL 1,737,199

INDICATING APPARATUS FOR LOCOMOTIVE BACK ERESSURE Filed Oct. 21, 1925 2Sheets-Shee1. 2

Patented Nov. 26, 1929 were EDVTIN S. PEARCE AND EDMOND C. KARIBO, OFINDIANAPOLIS, INDIANA INDIOATING APPARATUS FOR LOCOMOTIVE BACK PRESSUREApplication filed October 21, 1925. Serial No. 63,827.

Our invention relates to indicating apparatus for locomotive backpressure, and is particularly useful for indicating to the engineer howhe should move the reverse lever in order to maintain a substantiallyconstant back-pressure.

It will, of course, be understood that as the speed of the locomotiveincreases it is cus tomary to hook up or hook back the reverse lever 1norder to use the steam expansively and to reduce back-pressure in theexhaust line. Applicants have found, jointly with Mr. R. W. Retterer, asdisclosed in pending application No. 319,062, filed Aug. 22, 1919,

that for any given locomotive there is one particular back-pressurevalue, which, if held constant by adjusting the cut-off, will insure thedevelopment of maximum draw bar pull with the greatest degree ofeconomyand efficiency. In other words if the back-pressure attendantupon the most eflicient operation of the locomotive be ascertained andthe locomotive be operated constantly at that backpressure theefficiency of operation will always be at a maximum.

The primary object of our invention, therefore, is the provision of whatmight be termed a cut-off position change indicator, that is, amechanism which will give a positive indication at all times as towhether or not the reverse lever is in the best position for eflicientoperation of the locomotive, and further, to indicate directly whetherthe reverse lever should be hooked up or hooked down,

that is whether the cut-ofi' should be shortened or lengthened, to reachthe point of greatest efficiency for the particular conditions existingat'the time. Still another object of the invention is to indicate when a0 state of vacuum has been reached in the cylinders when the locomotiveis drifting.

A further object of the invention is the provision of means foraccomplishing the foregoing ends which shall at the same time be easy ofinstallation, inexpensive in upkeep and repair, readily adjustable tosuit the requirements of the individual locomotive, stable in operation,and extremely rugged to K withstand the shocks incident to the heavyexhaust pressure pulsations.

How we attain the foregoing advantages and others which will occur tothose skilled in the art will appear from the following description ofthe present'preferred embodiment of our invention and its operation,reference being had to the accompanying drawings, wherein:

Fig. 1 is a longitudinal section of the gauge proper;

Fig. 2 is a cross section of the same,-taken so on the line 2-2 of Fig.1;

Fig. 3 is a view partly in section, of the pressure impulse dampenerused in conjunction with the gauge; and

Fig. 4 is a diagrammatic view of a locomotive with our invention appliedthereto.

Referring now to Fig. 1, in which the letter A refers to the lower, oractuating part of the gauge as a whole, and B the upper, or

indicating part, back-pressure is admitted as through the pipe 2, fromthe choke or impulse dampener -D (shown in Figs. 3 and 4), into thepressure chamber 3, which is a space bounded by the head 4 and thesylphon or flexible bellows diaphragm 5. The pressure m in this chamber3, acts to expand the sylphon 5 against the counter-balancing pressureof the spring 11 later referred to. The movable end of the sylphon isattached to the annular block piece 6 mounted fast on the rod 7 andsicadapted to abut against the shoulder f the collar 9. This collar 9,whenthe back-pressure acting against it through the sylphon 5 andassociated parts is less than a certain predetermined amount is held bya rib or shoulis der 10 against the pressure of spring 11 supported bythe collar 12 threaded on the shank or spindle 18. Collar 12 may bescrewed one way or the other, by means of the key pin 14: fitting theholes 1 1, to adjust the compression of spring 11. s 7 I To preventpulsating movements and undue shocks in the apparatus from the changesin pressure caused by the intermittent exhaust of the locomotive, wehave provided, inaddition to the pressure impulse dampener D (elsewheredescribed in detail), a dashpot composed of the piston 15, fastened toone end of the rod 7 and operating in the cylinder '16. I There isprovided a port 17, in one end. of the cylinder, opening to theatmosphere, and the usual restricted passage 18 through the piston.Lubrication is provided by the oil cup 19.

The combination in our device of a sylphon and dashpot constructionmakes it both rugged and accurate, the dashpot piston serving to-dampensudden movements of the device, while at the same time the sylphon actswith sufficient force to move the indicator with accuracy against anyfriction that may exist between the dashpot piston and cylinder;

Within the sylphon 5 is a light spring 20 abutting against the face 21inside the cap 4 and acting against the portion 6 of the block 6 to keepthe block against theshoulder 8 when the back pressure is substantiallyat zero.

The indicator B, of the-apparatus (see Figs. 1 and 2) is of thefollowing construction: An arm 22, supported by a pivotmember 23 mountedon the pins 24, carries at itsend-a pointer 25 adapted to move over thedial 26. Below the pivot line the pivot-member carriesaroller 27 mountedon the pin 2?,

adapted to engage an annulargroove 28 in the block 6. A spring 29 on onepivot pin 24 exerts a slight pressure-onthe end of member 23 to keep theindicator-arm 22 in proximity to the dial. 7 Suitable marks 30 and31on-the dial indicate respectively zero back-pressure and hold position,hold position being an index of the amount of back-pressure when cut-01fisadjusted .to the position for greatest economy-and efliciency ofoperation Suitable directions to the engineman may also be marked on thedial, such as the words Hook down placed between-the points 30 and 31,Hook up placed to the right of point 31, and Vacuum placed to the leftof point 30.

The gauge has a base portion 32 with bolt holes 33 for convenientmounting on a bracket or other suitable support in the cab of thelocomotive. Fig. 4 shows the indicator mounted-on a locomotive withinthe ready observation of the engineer-and illustrates the connection ofpipe 2-through the dampener D to all four exhaust cavities of thecylinders through piping 34.

' The casing or Wall 35 isequip-ped 'at each end with a-cap piece 36,and "centered by these caps, within-the'cham'ber 37 thus formed, is a ofthe device, is the construction of the cappieces wl ich may be turnedthrough any degree relatlvely to each other or to the cylindrical shellwhile at the same time the planes of the inlet and outlet ports remainparallel, thus obviating the necessity for elbows and other fittings inthe connecting piping.

The construction of this, dampener, .per se, being a separate invention,forms the subjectmatter of a divisional applicatiom Serial No. 402,556,filed October 26th, 1929.

The operation of the complete apparatus follows:

Bacli-pressure, admitted from the exhaust ports of the cylindersthrough'piping 34 to pipe 2, must first pass through the impulsedampener D, to which it is admitted through one of the openings 42. Theimpulses pass ,ugh the choke passage or ,port 43, then through theopeningsof cylindricalscreen 33 into the chamber 37, back into thecentre the screen again on the other side of ring 39, and outthrough'theother port 43, which, widening outwardly, acts to reduce thevelociu'y of the now smoothed-out pressure stream as it leaves thedampener.

The dampened exhaust, or mean average exhaust pressure, is next passedthrough the pipe 2 to the actuating mechanism A of the gauge in thelocomotive cab. hen the pres sure enters the chamber 3 the sylphon 5expancs, moving to the left the block 6, the collar 9 and the rod 7.against the pressure of the spring 11, the dashp-ot on the remote endrod 7 assisting in dampening any pulsating movement remaining in theexhaust pressure line. The roller 27 engaging the groove in the block 6will be moved a corresponding distance and the pointer 25 will be movedover the dial towards the right.

Let us suppose that the particular locomotive to which the device'isapplied operates most efficiently with a back-pressure of ten pounds.For this installation, collar 12 should be adj ustcd on the spindle 13togive spring 11 the proper resistance to balance the pointer at the mark31 against a backpressure of 10 pounds persquareinch. [This mark 31 ishold position, and in actual operation when the pointer moves up to thatpoint it willindicate to the engineman that the conditions thenexisting. V After the tension on spring 11 has been thus properly'adJusted, when the locomot ve is the reverse lever isin the properposition for started, the reverse lever will be left in the position oflongest cut-off, or down in the corner as it istermed, until thepressurein chamber 3 builds up to 10 lbs. per square inch, in which time thepointer will have moved up to the hold point 31 on the dial. Shouldback-pressure increase beyond this point, the pressure in chamber 3 willincrease causin a movement of the pointer to the right of point 81 andgiving a hookup indication to the engineer, who then hooks up thereverse lever, shortening cut-off until the pointer returns to holdposition, the shortening of the cut-off, of course, cting toreduce theback-pressure. The reverse lever will be held in that position until thepressure changes again at which time it will be readjusted as indicatedby the pointer, hooked up if the pointer has moved again to the right ofmark 31, or hooked down if it has moved to the left. Guided by theseindications the engineman will so operate the reverse lever as tomaintain the pointer at the mark 31 on the dial, and in consequence theengine will at all times be operating at maximum efficiency.

For positive values of back-pressure the operation of the apparatus willthus be seen to be dependent upon the relation of the pressure inchamber 3 and the opposite pressure of the spring 11, but when thebackpressure falls below zero, viz., when a partial vacuum is created inthe locomotive exhaust passages, (as when the locomotive is drifting)the sylphon 5 is contracted, pulling the block 6 away from the shoulder8 against the pressure of the spring 20, and moving the pointer belowthe mark on the dial. This indicates to the engineman that the throttleopening should be greater or a longer cutoif should be used, to destroythe vacuum.

Ne claim 1. An indicator by which to regulate locomotive valve-gearcut-off adjustment comprising a dial having cut-off change indications,an arm cooperating therewith, actuating mechanism for the arm under theinfluence of the locomotive back-pressure, means yieldingly acting onsaid mechanism in opposition to said pressure, and damping meansco-operating with the mechanism and yieldingly resistive to changes ofposition thereof.

2. An indicator by which to regulate locomotive valve-gear cut-offadjustment comprising a dial having cut-off change indications, an armco-operating therewith, actuating mechanism for the arm under the infiuence of the locomotive back-pressure,

' means yieldingly acting on said mechanism in opposition to saidpressure, and damping means co-operating with the mechanism andyieldingly resistive to changes of pressure.

3. A pressure gauge comprising, in combination, a movable memberyieldingly resistive to pressure in one direction of its movement, meansco-operating therewith and yieldingly resistive to changes of pressurein either of two opposite directions of movement of said member, and anindicator actuated by said member.

a. in a locomotive, mechanism for indicating change of cut-off necessaryfor efficientoperation comprising a dial having-cut-off changeindications, an arm cooperating therewith, and actuating mechanismengagthe arm and consisting of oppositely-acting tension devices andmovable means positioned by said tension devices and actuated by thelocomotive back-pressure.

5. Mechanism of the character described comprising in combination withan indicator, actuating mechanism therefor comprising a reciprocablemember, a flexible member adapted to move it in response to variationsin locomotive back-pressure, and a tensioir device adapted to resistsuch movement, said reciprocable member having freedom of movementbeyond the range of said tension device. i

6. Mechanism of the character described comprising in combination withan indicator, actuating mechanism therefor comprising a rcciprocablemember, a flexible member adapted to move it in response to variationsin locomotive back-pressure, a tension device adapted to resist suchmovement, and damping means directly associated with the reciprocablemember.

7. In indicating apparatus, the combination of a movable member,indicating means actuated thereby, means for admitting pressure fluid tosaid member, means for clamping the movement of said member, and meansfor damping impulses in the pressure fluid admitted to the member.

8. In indicating apparatus, the combination of a flexible bellowsdiaphragm, indicating means actuated thereby, inlet means for admittingback-pressure to said-diaphragm, a dampener com'prisinga dash-pot andpiston with one of said elements connected to said diaphragm, and chokemeans co-operating with said inlet means for dampening the impulses ofthe back-pressure admitted.

9. In apparatus for indicating required changes in locomotive cut-ofi',the combina tion, with an indicator, of operating mechanism thereforcomprising a sylphon, a movable rod, a block fast thereon attached tothe sylphon and in operative engagement with the indicator, a collarloose on said rod, a spring acting on the collar to force it againstsaid block, and a stop in the path of said collar.

10. In apparatus for indicating required changes in locomotive cut-off,the combination, with an indicator, of operating mech anism thereforcomprising a sylphon, a movable rod, a block fast thereon attached tothe sylphon and in operative engagement with the indicator, a collarloose on said rod, a

spring acting onthe collar to force it against said block, a stop in thepath of said collar, and a dash-pot piston on said rod.

11. In apparatus for indicating required changes in locomotive cut-ofi,the combination, with an. indicator, of operating mechanism thereforcomprising a sylphon, a movable rod, a block fast thereon attached tothe sylphon and in operative engagement With the indicator, a collarloose on said rod, a spring acting on the collar to force it againstsaid block, a stop in the path of said collar, and a second springacting against said block in a direction opposite to said first spring.

12. In apparatus of the character described, the combination,with' anindicator, of operating mechanism therefor comprising .a sylphon, meansfor admitting locomotive back-pressure thereto, a movable rod,a blockfast thereon attached to the sylphon and in operative engagement withthe indicator, a collar loose on said rod, a spring acting on the collarto force it against said block, stop in the path of the collar, a secondspring acting against said block in a direction opposite to said firstspring, a dashpot cylinder and a piston on said rod Working in saidcylinder.

In testimony whereof, We have hereunto signed our names.

EDWIN S. PEARCE. EDMOND G. KARIBO.

